The movement and morphological changes of single cells in the corneal stroma of the living mouse will be observed under a fluorescence microscope. The behavior of normal cells as well as those in the neighborhood of a mild, circumscribed, injury will be followed. The injury will consist of a small circular epithelial debridement or the introduction of hydrogen ions by iontophoresis over a 0.4 mm circle, both of which are reproducible. The keratocytes and other stromal cells will be followed by the use of transgenic mice engineered to express fluorescent proteins ubiquitously, or by staining with nuclear or cytoplasmic fluorescent dyes. Leucocytes will be labeled with nuclear dye systemically. The images are recorded by a digital camera and time-lapse sequences are constructed for analysis. The mechanisms of cell death, activation and repopulation after a mild injury, will be characterized and analyzed. It is intended that further studies will lead to a clarification of the entire wound healing process in the cornea. It has an immediate relevance to the healing of surgical incisions and laser ablations made in the course of refractive surgery. Since the reactions of cells to injury in all tissues is likely to be similar, the results should have a wide significance.